/*	$OpenBSD: comm.c,v 1.10 2015/10/09 01:37:07 deraadt Exp $	*/
/*	$NetBSD: comm.c,v 1.10 1995/09/05 19:57:43 jtc Exp $	*/

/*
 * Copyright (c) 1989, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Case Larsen.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "compat.h"
#include <err.h>
#include <limits.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MAXLINELEN (LINE_MAX + 1)

char *tabs[] = {"", "\t", "\t\t"};

FILE *file(const char *);
void show(FILE *, char *, char *);
void usage(void);

int main(int argc, char *argv[]) {
  int comp, file1done, file2done, read1, read2;
  int ch, flag1, flag2, flag3;
  FILE *fp1, *fp2;
  char *col1, *col2, *col3;
  char **p, line1[MAXLINELEN], line2[MAXLINELEN];
  int (*compare)(const char *, const char *);

  setlocale(LC_ALL, "");

  flag1 = flag2 = flag3 = 1;
  compare = strcoll;
  while ((ch = getopt(argc, argv, "123f")) != -1)
    switch (ch) {
    case '1':
      flag1 = 0;
      break;
    case '2':
      flag2 = 0;
      break;
    case '3':
      flag3 = 0;
      break;
    case 'f':
      compare = strcasecmp;
      break;
    case '?':
    default:
      usage();
    }
  argc -= optind;
  argv += optind;

  if (argc != 2)
    usage();

  fp1 = file(argv[0]);
  fp2 = file(argv[1]);

  /* for each column printed, add another tab offset */
  p = tabs;
  col1 = col2 = col3 = NULL;
  if (flag1)
    col1 = *p++;
  if (flag2)
    col2 = *p++;
  if (flag3)
    col3 = *p;

  for (read1 = read2 = 1;;) {
    /* read next line, check for EOF */
    if (read1)
      file1done = !fgets(line1, MAXLINELEN, fp1);
    if (read2)
      file2done = !fgets(line2, MAXLINELEN, fp2);

    /* if one file done, display the rest of the other file */
    if (file1done) {
      if (!file2done && col2)
        show(fp2, col2, line2);
      break;
    }
    if (file2done) {
      if (!file1done && col1)
        show(fp1, col1, line1);
      break;
    }

    /* lines are the same */
    if (!(comp = compare(line1, line2))) {
      read1 = read2 = 1;
      if (col3)
        if (printf("%s%s", col3, line1) < 0)
          break;
      continue;
    }

    /* lines are different */
    if (comp < 0) {
      read1 = 1;
      read2 = 0;
      if (col1)
        if (printf("%s%s", col1, line1) < 0)
          break;
    } else {
      read1 = 0;
      read2 = 1;
      if (col2)
        if (printf("%s%s", col2, line2) < 0)
          break;
    }
  }

  if (ferror(stdout) || fclose(stdout) == EOF)
    err(1, "stdout");

  exit(0);
}

void show(FILE *fp, char *offset, char *buf) {
  while (printf("%s%s", offset, buf) >= 0 && fgets(buf, MAXLINELEN, fp))
    ;
}

FILE *file(const char *name) {
  FILE *fp;

  if (!strcmp(name, "-"))
    return (stdin);
  if ((fp = fopen(name, "r")) == NULL)
    err(1, "%s", name);
  return (fp);
}

void usage(void) {
  (void)fprintf(stderr, "usage: comm [-123f] file1 file2\n");
  exit(1);
}
